1. Field of the Invention
This invention relates to cartridge valves generally and, more particularly, to a novel cartridge valve that eliminates the need for O-ring seals in critical areas, as are now employed in conventional cartridge valves, and to such a novel cartridge valve that may include control functions such as metering and fluid control within and/or on the cartridge valve itself.
2. Background Art
Although cartridge valves may be found in many applications, they are especially useful and economical in hydraulic control applications where there are a number of control functions to be serviced. Some such applications are found in fluid power and fluid control systems as used in industrial, mobile, marine, aircraft, and space vehicles, for example. Prior to the use of multiple cartridge valves, individual valves were employed which required a substantial amount of piping and associated fittings. With the use of multiport cartridge valves mounted in a common manifold block having appropriate internal passages, piping is greatly simplified and a more compact and economical installation results. Equally as important, should a valve need to be replaced, it is a simple matter to remove the cartridge valve from the block and replace it with another without having to disassemble any piping. This not only saves time, but also eliminates an opportunity for leaks to develop which may happen any time that piping is disassembled and reconnected.
Typically, a cartridge valve, for example of the sliding spool type, comprises a solid cylindrical spool having a series of alternating lands and valleys, which spool is adapted for axial movement within a close fitting ported generally round, hollow sleeve. The ports on the sleeve are typically associated with internal passages of a manifold block and are arranged as necessary for the function serviced. The lands on the spool redirect the flow of a fluid as the spool slides axially in response to a spool-position control mechanism.
Sealing between the outer peripheral surface of the sleeve and the bore in which the valve is positioned is accomplished by O-rings inserted in raised circumferential annular grooves formed along the periphery of the sleeve between ports or groups of ports. These O-rings engage and are deformed by the bore of the block and thus seal one port or set of ports from adjacent ones. While these O-rings can provide a satisfactory seal, they have several disadvantages. Among these are that the seals must be carefully chosen to be compatible with the fluid to be contacted in the valve and a choice for one fluid may prevent the use of another fluid with the same valve. Also, even if compatible with a fluid, there may be aging and/or chemical degradation over time. Another disadvantage is that the ports and grooves in the manifold when formed are sharp-edged and tend to cut the O-rings as the cartridge valve is inserted. This will remain undetected until the valve is tested or placed in service, or, even if it passes a test, may lead to early failure. To minimize this problem, the edges of the ports and grooves must be stoned or deburred to provide a less sharp edge. Also, deep cavities are difficult to inspect. Of course, installation of the O-rings requires careful labor and the O-rings also take up space.
In many fluid control systems, certain control functions are required, such as, metering, bleeding, directional control, check valving, and pressure reduction. Typically, these control functions are handled by separate discrete components which are interconnected by piping. Such an arrangement is relatively expensive and introduces into the system additional potential points of leakage and failure at the connection points. Servicing is also complicated by the necessity of having to break these numerous connections and having to reconnect them which may result in an unsatisfactory, leaking connection.
Accordingly, it is a principal object of the present invention to provide a cartridge valve constructed without O-rings in critical areas.
Another object of the present invention is to provide such a cartridge valve that is simple and economical to construct.
An additional object of the present invention is to provide such a cartridge valve that may be used with a wide range of fluids without the necessity of changing any components thereof.
A further object of the present invention is to provide such a cartridge valve which may, alternatively, either have a shorter length, for a given fluid flow, to make it more compact and economical for lighter manifold housings, or, for a given length, to increase the inlet and outlet sizes of the ports to allow higher flow rates and/or lower pressure drops of the transit fluid.
Yet another object of the present invention is to provide such a cartridge valve that eliminates the damage to O-rings presently occurring during repeated removal and insertion of cartridge valves for inspection, troubleshooting, etc.
Yet an additional object of the present invention is to provide such a cartridge valve that may be used with conventionally constructed manifold bodies.
Yet a further object of the present invention is to provide such a cartridge valve that may include a variety of fluid control elements within the valve itself.
Other objects of the present invention, as well as particular features and advantages thereof, will, in part, be obvious and will, in part, be apparent from the following description and the accompanying drawing.